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mikegc asked

Using Tesla battery with Multiplus 5000 24v ESS - Your experience

I’m looking for anyone who has experience of using a Tesla battery module(s) with a Multiplus and is willing to share their views on:

1. What BMS they have used, how it was connected, configured and how well it maintains cell balance together with any positive or negative points.

2. Battery Protection - how they have protected the system in terms of Over/Under Voltage and Over/Under Temperature and what devices used.

3. Configuration, Assistant and other parameter settings used.

4. A schematic of their setup.

5. Any other views or observations like don’t even think about this or its the best thing I did.


My current setup is running ESS using a Multiplus 5000 24v, CCGX, 3.8kw solar via grid connected inverter, 12x2v lead acid cells (old and dying).

Many thanks

Mike

Lithium Battery
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4 Answers
mike-deau avatar image
mike-deau answered ·

I can help with some of this as I am putting together a couple of Tesla systems right now.


1. What BMS they have used, how it was connected, configured and how well it maintains cell balance together with any positive or negative points.

I am using a SimpBMS to chat directly with the tesla batteries over CAN. It then can be lined to a GX device (in my case a cerbo) over BMS-CAN. The battery array will show up and populate a whole bunch of fields with useful bits.

On balance. The cells stay pretty well balanced on their own. I have gone though only a couple charge cycles but without a BMS they stayed at ~11mv. SimpBMS takes care of the balance for me at a setting you choose. I set it to 10mv.


2. Battery Protection - how they have protected the system in terms of Over/Under Voltage and Over/Under Temperature and what devices used.

I have several layers of protection for this. There is a main contactor run off the BMS that will close if any alarms are triggered. These alarms are set at values that are slight higher/lower than is set...

On the MP 3000 for AC loads, a BP100 Smart for DC loads and my MPPT solar charger. In theory (and so far in practice) the victron components disengage before the BMS throws the switch.

3. Configuration, Assistant and other parameter settings used.

If you get this far and want to proceed I can help with this, but see answer 4.

4. A schematic of their setup.

Check out this setup. https://www.mortonsonthemove.com/toms-tech-blog/updated-tesla-module-rv-installation

Not me, but it is the only intro out here to this topic (I know you are a static install, it still helps). I can provide a schematic when mine is complete and checked for errors so I don't give out anything too embarrassing.

5. Any other views or observations like don’t even think about this or its the best thing I did.

If treated well and not over/undercharged my opinion (for what it is worth) is that these are the best price to performance out there. You just need a bit of knowledge and to proceed with safety as your first priority.


Second extra credit thought is that the reason I went with the SimpBMS is that I can connect as many Tesla Modules as I wish. So for one fixed cost, I get to implement as many (in my case 4) modules as you like and all of the info for each pack is monitored with most of it ending up in the Victron universe.


Hope this helps.


Mike



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intra avatar image intra commented ·

Are you able to discharge the cells lower than 3.4v (20.4v) ?



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snoobler answered ·

Haven't done it , but I've seen some limitations with other's setups.


1. There are many 6S BMS available. The trick is to find one that can handle the current you need. MANY run these without a BMS. With a 5kW system, you'll be looking to pull 200A, and there are very few cheap BMS that will do this. If you want to invest in a BMS that costs hundreds, then there are good options out there.

2. If you use a BMS, these are trivial. Most just rely in inverter cut-off and charge controller cut off. Operate the cells in a range that is well inside its max.

5. The issue with the 6S modules is they they are more of a 22V system than a 24V system. When fully charged, they're only 25.2V. When fully discharged, they're around 18V. Most inverters cut off around 21V. This gives you a very narrow range, and it doesn't allow for full utilization of the pack capacity. You likely only have access to about half of it.

There are many "powerwall" type options at bigbattery.com that are LFP. They are very cost effective when compared to the Tesla packs. Most have an integral BMS, but they may not meet your current requirements for a 5kW unit.

Might be worth a search and query at http://diysolarforum.com/



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Justin Cook avatar image
Justin Cook answered ·

@MikeGC, I will add a cautionary note here that Tesla batteries are not supported and are strongly discouraged for use with Victron components (and I personally discourage them for use with any components other than Tesla OEM BMSs and active cooling systems), largely because of their propensity toward thermal runaway if not very carefully treated.

...that is not to say that it cannot be done, but it must be understood that you do so at your own risk and at the risk of your device warranty, and really basically should not be done.

Unlike the stable LFP chemistry, Tesla cells (recent) are NCA which, while having much higher energy density than LFP, are also capable of bursting into flame when overcharged/overheated, and a burning NCA battery is effectively inextinguishable. Adding to the odds of catastrophic failure is the fact that Tesla batteries are also sub-normal voltage: a "24v' Tesla battery generally sits around 25v at the very top end, which makes it incredibly easy to overcharge it with a device intended to be used on a common 24v nominal bank that wants to be charged around 28.8v.

Bottom line: I know the price point is tempting. But please don't.

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intra avatar image
intra answered ·

1. What BMS they have used, how it was connected, configured and how well it maintains cell balance together with any positive or negative points.

I am using a Batrium WM5 thats talking CAN & DVCC to a connected MP2 3K via a Venus GX.

Cell are very closely balanced to 0.03-0.04v


Pos: Its an Australian product and is feature rich.


2. Battery Protection - how they have protected the system in terms of Over/Under Voltage and Over/Under Temperature and what devices used.

BMS monitors the battery, when charge reaches 4.15v multi turns off. At 4.17v or 3.20v BMS cuts off the battery pack via an ABB breaker connected to the main DC cables that run to the Multi.


3. Configuration, Assistant and other parameter settings used.

ESS Assistant


5. Any other views or observations like don’t even think about this or its the best thing I did.

Learnt alot, one of the most interesting projects to be involved in.

There are a few things that still a little confusing, such as being able to discharge lower than 3.4v per cell. I think there's a hard limit and it would be great if someone from Victron could confirm this.




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